1. Field of the Invention
The present invention relates to an image forming device, and more particularly to an image forming device which has a function of managing operating information.
2. Description of the Related Art
In image forming devices which form (i.e. print) images on sheets of paper (such as a multi function peripheral (MFP) provided with the scanner function, facsimile transmitting/receiving function, copying function, function as a printer, data communicating function, and server function, a facsimile machine, a copier, a printer, and the like), motors are used to generate driving force for use in image formation. The motors may include, for example, a motor which drives rollers transporting a sheet of paper, a motor which drives a print engine unit, and others.
FIG. 8 is a block diagram showing, by way of example, the circuit configuration of a drive system in a conventional image forming device.
The image forming device includes a power source unit (low-voltage power source unit) 800, a drive unit 810, and a control unit 820. Drive unit 810 and control unit 820 are driven by electric power supplied from power source unit 800.
Power source unit 800 is driven by commercial power supply input from a power plug 801. Power source unit 800 includes a main power switch 803, a rectifying unit 805, and a DC-DC converter 807. Main power switch 803 switches between on/off of input of AC power supply. Power source unit 800 converts the input alternating current to direct current at rectifying unit 805, and coverts the voltage of the direct current at DC-DC converter 807 for output. DC-DC converter 807 outputs a voltage of 24 V DC to drive unit 810, and outputs a voltage of 3.3 V DC to control unit 820.
Drive unit 810 has motors 811-815. Motors 811-815 supply driving force for use in a paper transporting operation and other printing operations. Motors 811-815 are each supplied with the direct current output from DC-DC converter 807 and driven under the control instructions from control unit 820.
Control unit 820 includes a control device 821 and a non-volatile memory 823. Control device 821 communicates with non-volatile memory 823 to read control programs therefrom and write data thereto, for control of drive unit 810 and other sites in the image forming device.
Control device 821 performs management of operating information of the image forming device. Such management of the operating information includes life management for a consumable product 830 such as a toner cartridge. The management of the operating information is performed for example in the following manner. Control device 821 backs up the operating information in non-volatile memory 823 or in a non-volatile memory 831 provided within consumable product 830. The operating information backup process is performed every time a predetermined number of times of printing are finished. The operating information may be a count value of the total number of printouts which is obtained by summing up the number of times of printing. When the count value as the operating information has reached a predetermined reference value, control device 821 determines that the life of that consumable product 830 is over.
When such a backup process is performed frequently (every time one page is printed, for example), the processing load on control device 821 increases. On the other hand, when the backup process is performed every time one job is finished, for example, the processing load on control device 821 may be decreased. Reduction of the processing load exerted on control device 821 allows use of an inexpensive device for control device 821. This can also reduce the electric power consumed by the image forming device.
Document 1 below discloses an image forming device which, when a main power switch is turned off, provides a display attracting a user's attention with LEDs or buzzer on a display unit in the device. For providing the attention-attracting display, the image forming device uses counter electromotive force by a polygon motor which keeps rotating due to inertia, to thereby cause the polygon motor to stop earlier. Furthermore, by providing the attention-attracting display, the image forming device prevents vibration or shock from being applied to the device until the polygon motor is stopped. Accordingly, the image forming device prevents damages to the polygon mirror unit.
Document 2 below discloses an image forming device in which a secondary battery is charged with counter electromotive force or regenerative electric power in an actuator such as a motor. When starting a motor or the like, the image forming device causes the secondary battery to operate as an auxiliary electric power source, thereby reducing the load on the AC power line. The image forming device can efficiently charge the secondary battery with the regenerative electric power and the like.    [Document 1] Japanese Patent Application Laid-Open No. 9-185004    [Document 2] Japanese Patent Application Laid-Open No. 2007-178639
In the image forming devices as described above, electric power supply to a motor may be stopped for example when a main power supply is turned off or when electric power supply to the image forming device is stopped due to a power failure or the like. When the electric power supply to the motor is cut off during printing, the motor is stopped and, thus, the operation is stopped in the middle of the image forming operation. For example, in the image forming device having the circuit configuration as described above in conjunction with FIG. 8, when electric power supply from the commercial power supply is stopped due to a power failure or the like or when the supply from the commercial power supply is cut off as main power switch 803 is turned off, the DC voltage is no longer output from power source unit 800 to drive unit 810 and control unit 820. This causes motors 811-815 to stop, because they are driven by the voltage of 24 V DC supplied from power source unit 800. Similarly, control unit 820 stops operating, because the voltage of 3.3 V DC is no longer supplied thereto. As a result, no driving force is provided from motors 811-815, and no control is performed by control unit 820, whereby the image forming device stops operating.
When the image forming device stops operating as described above, the process for backing up the operating information suffers the following problems. Life management of consumable product 830 will now be described by way of example. During the image forming operation, toner is consumed and a photoreceptor wears or deteriorates due to mechanical stress and the like, so that the life status of each component changes constantly. In the case where the operating information (i.e. life information) recorded on non-volatile memory 831 is supposed to be updated upon completion of each job, for example, if power supply from the electric power source is stopped during the image forming operation, the life information backed up in non-volatile memory 831 may become different from the actual life status. That is, when power supply from the electric power source is cut off in the middle of the operation, any change in life status from when the operating information was lastly updated to when the electric power supply is cut off would not be reflected to the life information stored in non-volatile memory 831.
As the number of times of cutoff of the power supply from the electric power source increases, the difference between the life information being backed up and the actual life status increases cumulatively. As a result, consumable product 830 of which life has actually expired may be determined that it has not yet reached the end of the life on the basis of the backed-up life information. In this case, consumable product 830 is used beyond its life, hindering appropriate formation of images.
If the life information is updated frequently, the above-described error will become small. This however leads to increased processing burden on control device 821, as described above. If an electrical storage device such as a battery or a capacitor is provided so as to use the electric power supplied therefrom for updating the life information, the error as described above will not occur. This however increases the manufacturing cost of the image forming device.
Furthermore, the reference value used for determination of life may be set to have a large margin with respect to the actual life, taking the above-described error into consideration. This ensures that consumable product 830 is used within its actual life, even in the presence of the error as described above. Setting such a large margin for the life reference value, however, raises the need to produce consumable product 830 having a life longer than the reference value, which increases the manufacturing cost of consumable product 830.
This problem will now be described by giving a photoreceptor as a specific example of consumable product 830. For management of the life status of the photoreceptor, the rotation time of the photoreceptor is stored in its non-volatile memory 831. The rotation time of the photoreceptor is the life information and the operating information for the photoreceptor. When main power switch 803 is turned off or a power failure takes place, the change in status from when the life information was lastly written will not be reflected to the life information. Thus, it is preferable that the information is written into non-volatile memory 831 at shorter intervals. Writing at such shorter intervals, however, increases the processing load on control device 821. Accordingly, in the practical life management, the rotation time of the photoreceptor is backed up in non-volatile memory 831 every time it rotates for 60 seconds, for example.
In such a case that the backup process is conducted for every 60 seconds of rotation, assume that power supply from the electric power source is cut off as described above, while the image forming device is operating, after a lapse of 30 seconds from the previous backup operation. In this case, the photoreceptor's rotation time which is being backed up in non-volatile memory 831 becomes 30 seconds shorter than the actual driving amount of the photoreceptor. If such an error is accumulated repeatedly, the error therebetween becomes large.
For example, suppose that the photoreceptor has a life (i.e. driving time) of 2,000 minutes. Assuming that one page can be printed with six seconds of driving, 20,000 pages may be printed within the life. This numerical value is written in a product catalog, for example. Assuming that 100 pages are printed each day, the photoreceptor is driven 10 minutes per day. In this use environment, if the cutoff of the electric power supply that would cause an error in driving amount of 30 seconds occurs once every day, the actual driving amount of the photoreceptor becomes greater by 5%.
In the case where a margin is set for the life reference value taking such an error into consideration as described above, when the actual life is 20,000 pages, the life reference value needs to be set to about 19,000 pages. In other words, in order to secure 20,000 pages as the life reference value, it is necessary to use a photoreceptor that can actually last for the number of pages increased by 5%, or 21,000 pages. This eventually increases the manufacturing cost of the photoreceptor.
The problem as described above not only occurs in life management, but commonly occurs in management of the operating information for control of the image forming device. That is, when power supply from the electric power source is cut off as described above, there occurs an error between the actual operating status and the operating information backed up in the non-volatile memory. Such an error may cause malfunction, and increase the cost for preventing the same.
Neither Document 1 nor Document 2 above discloses any effective solution to such a problem that the operating information differs from the actual operating status.